Apparatus for mixing the vapor of a volatile anesthetic



y 5, 1951 w. EDMONDSON ET AL 2,553,446

APPARATUS FOR MIXING THE VAPOR OF A VOLATILE ANESTHETIC Filed Nov. 30,1949 3 Sheets-Sheet 1 May 15, 1951 w. EDMONDSON ET AL 2,553,446

APPARATUS FOR MIXING THE VAPOR OF A VOLATILE ANES'II-IETIC "May 15, 1951w. EDMONDSON ET AL 2,553,446

APPARATUS FOR MIXING THE VAPOR OF A VOLATILE ANESTHETIC Filed Nov. 50,1949 3 Sheets-Sheet 5 Inventor Patented May 15,1951 v T5.

APPARATUS FOR MIXING THE VAPOR OF A VOLATILE ANESTHETIC WilliamEdmondson and Wilfred Jones, Oxenhope, Keighley, England ApplicationNovember 30, 1949, Serial No. 130,293 In Great Britain October 27, 19483 Claims. 1

This invention relates to apparatus for mixing the vapour of a volatileanaesthetic such for example as trichlorethylene with air for inhalationpurposes by a patient.

Existing apparatus for the purpose is open to the objection that thepercentage of trichlorethylene in the trichlorethylene air mixtureincreases with increasing temperature owing to the increase in thevapour pressure of the liquid trichlorethylene with temperature.

The present invention has for its object to introduce a device which asthe temperature of the apparatus rises, reduces the area of an orificethrough which concentrated trichlorethylene air vapour issues whilekeeping constant, or increasing the area of an orifice through which thediluting air is drawn.

According to this invention the apparatus comprises a vessel in which aquantity of the liquid can be placed, the said vessel being providedwith an air inlet for providing air for vapourizing the anaestheticliquid, the apparatus being provided with a diluting air inlet and atemperature controlled device which as the temperature of the apparatusrises from any cause automatically reduces the orifice through which theconcentrated volatile anaesthetic air vapour issues while keepingconstant or increasing the area of the orifice through which thediluting air is drawn during inhalation through a suitably arrangedinhalation outlet. The liquid may be absorbed by means of a wick orother absorbent contained in the vessel. The thermally operated devicemay be arranged to provide for automatically altering the relative areasof the orifice through which the concentrated volatile anaesthetic airvapour issues and the area of the orifice through which the diluting airis drawn during inhalation.

In order that the said invention may be clearly understood and readilycarried into effect, the

same is described more fully with reference to the accompanyingdrawings, in which:

Fig. 1 is a section of one form of appliance for carrying out theinvention.

Fig. 2 is a similar view showing a preferred form of appliance.

Fig. 3 is a section taken on line 33 of Fig. 2 looking in the directionof the arrow.

Fig. 4 is a front view of the appliance and Fig. 5 is a diagram showingthe circuit flow.

A form of appliance for carrying out the invention comprises a casing Afitted at one end with a perforated annular plate B which forms .acentralizing device and holder for a wick tube C that is packed with awick D or body of absorbent material that may extend from the bottom ofthe tube to within a short distance from the top say for example aboutan inch. The opening in the bottom of the wick tube may be contracted bya conical ferrule C which is fixed therein, and, fastened tothe'perforated plate, which may be slightly larger in diameter than thecasing is a cap E which may be formed with a circle of holes E in thebottom and with a ring of holes lilaround its periphery, and such capmay be fitted with an annular tray E which may be dished and formed witha flange E which extends around its opening and contacts with the end ofthe cap. Fixed to the upper end of the Wick tube is an annular plate Cin which is centrally fixed a mixing tube F of smaller diameter than thewick tube that projects through an opening in the top of the casing.Situated within this tube is a small tube G fitted at the bottom with aplate G that rests on the top of the Wick and formed in the tubeimmediately above such plate is a lateral opening G above which is acircular baffle plate G Fixed on the upper end of the small tube G is aflanged collar G that rests on a shoulder F in the mixing tube andscrewed into such collar is a nipple H that terminates at its upper endin a point H This nipple is formed with a central bore H with a lateralopening H which communicates with a dished recess G in the top of theflanged collar. The latter together with the pointed nipple forms thebottom of a chamber for a sealed glass phial J which may containtrichlorethylene.

The top of the casing is closed by a cover through which the phialcontaining portion of the tube passes and such cover is formed with acentral recss to receive a nut K which screws onto a threaded portion ofthe tube F and clamps a plate L together with a portion of the cover Abetween itself and a shoulder or abutment on the tube. diametricallyarranged lugs L L Pivoted in the lug L is a forked lever M which spansthe mixing tube F and is provided at its free end with a cross bar Mwhich extends through the prongs of the fork and forms an abutment for avery short arm N of a bell-crank lever that is formed with a long arm Nwhich is situated between the casing A and the mixing tube F and isprovided at its free end with a valve plate N which operates inconjunction with a seating F that is situated opposite to a lateralopening F in the tube and may form part of the wall of a cham This plateis provided with two this rod is also conical as shown at O or roundedand is supported in a bearing .0 which may form part of a screw that isscrewed'into aztapped hole in the perforated annular plate B.

To utilise the apparatus a glass phial .of trichlorethylene may beplaced in the chamber and the cap screwed down until the sharp .pointbreaks the glass. The liquid thus .rel'eased. runs down the small tubeand is absorbed by the wick.

If the latter has already been saturated'excessliquid will drain outthrough the holes at the bottomof the casing.

.Alternatively the .filling may be effected by .usingthecap at the top.of the phial chamber. as

.a measuring device for measuring theliquid.

Having charged the apparatusxthe inhalation outlet A isconnecteddirectlyto a mask which the-patient appliesto his face, or itis connected :to'oneend of. a flexible tube at the other end of .whichisanon-return valve and an exhalatory 'valveunit to which .is attached'theface .mask. Whenthe patient inhales, air is drawn through "theperforated annular plate and a portion of such air passes through the:perforations without .coming into contact with the liquid. Some of theair passes through the wick and picks up a highconcentration of theliquid vapour.

This

mixture enters the mixing tube and issues be- .tweenthe seating and thevalve plate and then mixes withthe outer stream of clear air.

The relative areas of the air holes in the-per- -forated plate and ofthe annular area between the seating and the valve plate are so adjustedthatat a given temperature the desired mixture is obtained. 7

If now the temperature and therefore the vapour'pressure of the'liquidrises, the area of the annular orifice is reduced.

The casing which may be made of brass expands while the length of therod remains approximately the same. Although the valve plate is tendedto be pushed on to its seating by the spring, it ishowever held in acertain positionthrough theacti-on of 'the lever mechanism andthepractically nonexpanding rod but as the length of the casing increasesthe spring causes the valve plate to move towardstheseating'thusreducing the annularor-ifice area until the levers are againpressing: upon the pivot of'therod.

This reduction of the area of the orifice passing strongtrichlorethylene vapour will cause a 'reduction of the proportionpassing into themix .ture: and will thus compensatefor the increasedstrength of this vapour .due .to the increased :vapour pressure of thetrichlorethylene.

The preferred form of appliance shown .in Figs. 2 and for carrying outthe invention .com-

:prises a.rectangular.case I to the base of which is "attachedat .0118end a vapourizingchamber 2 .which'is packed with a wick 3 or thelike and:contains vbafiles '4 to prevent splashing of the liquid anaesthetic.

This vapourizing chamheris also-fitted with av tube 5at right angles orthere- .abouts to the chamber for charging with the :anaesthetic.

The inlet-iof .:this::charging tube .is

-so arranged that when the instrument hori 4 zontal only a definitevolume of liquid can be poured therein.

Passing through the centre of the vapourizing chamber is a tube 6 of amaterial which has a high coeflicient of thermal expansion such forexample as brass. One end 6A of the tube is .opento' theatmosphereandtheother end is ex- :en'diofthe brass'tube which is open to theatmosphere' this rod rests on an adjusting screw I0 and its iotherendiprotrudes beyond the valve seat andnorm'ally tilts a valve I Islightly off the seat 1 so that it is kept clear or open in whichposition .it. is retained by means of a spring I2.

Also incorporated in the mixing chamber is an air inlet valve I3 whichmay be set in a more or less open position. For? this purpose it mayconsist of a flat disc heldon one side of aseatin I4 by means-of one ormore screws I5 and clear of the seating onthe opposite side by meansof-ascrew I6 which is adjustable so that the valve can be set to the desiredopening.

Connected to the mixing chamber isa rubber or other flexible tube I!Fig. 5 to which is at,- tached a face: piece adaptor I8 incorporateclinwhich are two non-:return valves 19,29. This valve I9 acts as aninspi-ratory valve which al.- lows the patient to inhale airandvapourirom the flexible tube and prevents expiration down the tube. Theother'non-z-return valve 2!] allows the patient to exhale to theatmosphere and prevents inspirationaof air'therefrom. .On the face pieceadaptor between thesetwo valves isza' branch pipe 2I onto which is:plugged the face piecei22.

On inspiration 'air enters one commonv inlet :23 into the :casing. Itthen divided :and;a;portion isdrawn through the end 16A ofthe brass tube:beyond'thevapourizingchamber and-as it passes throughsuch tubeiit isdeflected by apartition 63 therein .throughholes "60 in the tube, intothe vapourizing chamber'where itzcomeszinmorr- .tact with theisoakedwickand consequently picks up the anaesthetic 'vapour. It then :returnsthrough another set of :holes 613: in the 'brassitube ingof the: airinlet valve I3 and the anaesthetic inlet valve I I. As the atmospherictemperature. rises the trapour pressure of the anaesthetic "also risesand .tozprevent this resulting 'in an increased centage ofanaesthetic-to the patientthe anaes. thetic controlling valve I I is'made -to;close slightly as the temperaturerises: andzto openiasthecterrr- .peitature falls. This isrdue-sto-the .combined'action of theexpansion of the brass tube -li and negligible expansion ofzthe'ro'd'iland in this'way the gap between the seating 1 .andth'e' valve II isreduced.

.fIhiszarrangement :results in? a .zconsistentzmixture: of anaestheticvapour and/air to the patient irrespective of .ordinaryatmospherictemperature variations.

What we claim: as our." invention and? desire to secure by LettersPatent in the United States is:

1. Apparatus for mixing the vapour of a volatile anaesthetic with airfor inhalation purposes by a patient, comprising a vessel in which aquantity of anaesthetic liquid can be placed, the said vessel beingprovided with an air inlet for providing air for vapourizing saidanaesthetic liquid, a mixing chamber being provided with a diluting airinlet and an orifice communicating with said vessel, a temperaturecontrolled de' vice which as the temperature rises from any 3. Apparatusaccording to claim 1 wherein a thermally operated device may be arrangedto provide for automatically altering the relative areas of the orificethrough which the concentrated volatile anaesthetic air vapour issuesand of the diluting air inlet through which the diluting air is drawnduring inhalation.

WILLIAM EDMONDSON. WILFRED JONES.

REFERENCES CITED The following references are of record in the file ofthis patent:

15 UNITED STATES PATENTS Number Name Date 294,047 Hurd Feb. 26, 18841,257,934 Rund Feb. 26, 1918 1,323,181 Goodfellow Nov. 25, 19191,358,838 Fulton Nov. 16, 1920

